Self-Diffusion Coefficients and Rotational Correlation Times in Polar Liquids. III. Toluene

Abstract

The self-diffusion coefficient of liquid toluene has been measured from 175 to 380°K and is represented by (4.5± 0.6) × 10−3 × Exp[−(3.12± 0.10) / Rt] Cm2Sec−1. Relaxation time data of Woessner and Snowden and the pressure dependence of the ring proton relaxation rates of Parkhurst, Lee, and Jonas are interpreted by means of the quasilattice random flight model of liquids. Root-mean-square angles of reorientation are calculated for the ring and methyl protons from a hindered rotation model of liquid state reorientation. The pre-exponential factor for self-diffusion is calculated to be 2.9 × 10−3 cm2sec−1 from the quasilattice model for the self-diffusion coefficient. Volumes of activation for self-diffusion and the intramolecular relaxation rate are compared with experimental values. It is demonstrated that the microviscosity model of Gierer and Wirtz, which is often invoked to explain the magnitude of rotational correlation times, does not apply to most liquids.